Switching units for electrical switching devices, together with corresponding electrical switching devices are well-known in principle. They normally have a breaker mechanism with an operating lever. Furthermore, an actuatable switching mechanism which can be actuated by the operating lever is often provided for such a breaker mechanism. Over and above this, for the purpose of affixing the breaker mechanism, a breaker assembly board is generally provided, in particular with a plate-like format. The breaker mechanism is attached to this breaker assembly board, for example by means of rivets, which can function in addition as bearing points or bearing shafts, as appropriate.
A disadvantage of the known switching units is the fact that the positioning of the breaker mechanism within an electrical switching device, in particular within a housing of the electrical switching device, is only possible at considerable expense, or with a long tolerance chain, as applicable. Thus, in the case of the known switching devices, such as for power circuit breakers, the switching units are arranged in a lower housing part, onto which is fixed in turn an upper housing part.
However, the most accurate possible alignment of the breaker mechanism is desired, in particular of the operating lever or the switching mechanism, as appropriate. This is because, in the case of the known switching units, the movement of an operating lever and/or the movement of the switching mechanism can fulfill not merely one but two or even more functions. This means, for example, that mechanical interfaces are provided which, when the operating lever is moved between two positions, transfer the movement not only to the switching mechanism but also to another mechanism, for example an actuator.
In order to ensure that this transfer functions in a mechanically reliable way, the most accurate possible geometric positioning of the switching unit within the electrical switching device is of critical importance. However, if the positioning of the switching unit within the electrical switching device has several locating stops which are subject to tolerances, forming a tolerance chain, there is a danger that an insufficiently accurate positioning arises. This can only be avoided by specifying particularly close tolerance requirements for the individual components, so that the cumulative overall tolerance of this tolerance chain lies within the permissible range. This leads to high costs in the manufacture of the individual components, in particular for the switching unit, the housing components and other components of the switching device.